The present invention relates to a feed index device in a universal parallel ruler or the like to draw a plurality of lines at desired intervals with high accuracy.
In drawing a hatching which represent a section, dimension lines, ruled lines on slip or note, display of tiles in a building drawing etc., it is substantially more preferable with respect to accuracy and convenience to regulate an interval at which the scale of a universal parallel ruler is parallelly moved according to a desired set value than to move the scale according to eye-measurement or with use of a separate ruler for every line.
There have already been proposed devices for this purpose. For example, there is one in which a guide track is provided with a rack and a movable straight-edge carriage plate adapted to move along the rack. There is a pinion adapted to be engaged with said movable carriage plate so that a rotation of the pinion is multiplied and transmitted by a gear train to a rotatable index plate or table. Thus, a movement distance of the movable carriage plate may be visually determined according to a rotating angle set on the index plate or table. In another prior-art system a plurality of ratchet wheels of different pitches are coaxially mounted on a shaft which is rotated as a movable carriage plate moves and there are provided selectably engageable stoppers respectively in association with said ratchet wheels so that the movement of the movable carriage plate may be regulated by operation of the stoppers. The first of these prior-art systems is disadvantageous in that the movement distance of the movable carriage plate can be determined according to the rotating angle of the index table but it is impossible for the movable carriage plate to be automatically stopped for each predetermined movement distance thereof. The second system is also disadvantageous in that unpractically many ratchet wheels are required to regulate the movement distance of the movable plate according to a desired value and a mechanism for operation of the stoppers must be complicated, since the movement distance of the movable carriage plate is defined by the pitch intervals of the ratchet wheels.
It is the principal object of the present invention to provide, in view of the disadvantages of the prior art as mentioned above, a feed index device in a universal parallel ruler, or the like, which is simplified in structure and easy to handle; selectively adjustable so that the movement distance of a movable carriage plate (i.e., the movement distance of the straightedge) may be optionally selected; and automatic so that the movable plate is automatically stopped for every movement distance thus selected.